[kx250rider]

That's good news! I bet that some of that dimness is the cataract. Not a BIG factor, but every bit will help.

Blooming (picture gets BIGGER and dims from the center outward when turning brightness up) is caused by several things: First one I'd check is the filter caps. If they leak, your B+ is low, and the set will bloom. Also the 3A3, and possibly the damper and horizontal output tube will cause that. If it's just BLURRING with increased brightness (pic stays pretty much the right size), it's probably a gassy, weak CRT. Depending how bad, you can either add a brightener or even rejuvenate it. I wouldn't rejuvenate it though, unless/until you're willing & ready to have it rebuilt. Usually rejuvenating a 21" roundie is fine for about a year, but there's always a good chance that you'll kill it on the spot.

Do you have a high voltage probe? If so, measure the HV and see if it's dropping off when the picture blooms. It should drop slightly, but stay over 20KV or so. MY ADVICE: DO NOT INCREASE the HV adjustment!!!!!! Every time I've done that, the flyback has failed on me within a month, even if I'm just turning it up to where it's supposed to be!!!!! If the HV is low, leave it. If it's high, turn it down to 21KV.

Charles